Preparation of polymer solutions



, y 23, 1946- I R. R. MERNER 2,404,723

I PREPARATION OF POLYMER SOLUTIONS Filed Nov. 10, 1944 IINVENTOR.

ATTORJV Patented July 23, 1.946

ZAMJZE PREPARATION OF POLYMER SOLUTIONS,

Richard R. Merner, Deerfield, Ill., assignor to E. I. du Pont de Nemours & CompannWilmington, Del., a corporation of Delaware Application November 10, 1944, Serial No. 562,857

11 Claims.

This inventionrelates to a new composition of matter and shaped articles produced therefrom. More particularly, this invention relates to an organic solvent solution of polyacrylonitrile, i. e. polymerized acrylonitrile or polymerized vinyl cyanide (CH2=CHCN), and copolymers and interpolymers of acrylonitrile in which at least 85% by weight of the polymer is acrylonitrile; .and the production of shaped articles from. said organic solvent solution of said polymers of acrylonitrile.

Polyacrylonitrile, and copolymers and interpolymers of acrylonitrile with other polymerizable substances, for example vinyl or acrylic compounds in which at least 85% by weight "of the polymer is acrylonitrile have been known for some time and recognized as possessing desirable physical and chemical properties including toughness and insolubility in and insensitivity to common organic solvents such as methyl or ethyl alcohol, acetone, ethyl ether, ethyl acetate, hydrocarbon solvents, chlorinated hydrocarbons and the like. Because of these facts, numerous attempts have been made to form these polymeric materials into yarns, films and other shaped articles.

The copending application of George IL Latham, Serial NO. 562,012, filed November 4, 1944 discloses solutions of polyacrylonitrile in dimethyl carbamyl compounds and the production of extruded and otherwise shaped articles and structuresfrom such solutions. The abovesaid application of George H. Latham represents the first successful dissolution of polyacrylonitrile in a solvent to produce a solution which is suitable for the production of commercially useful textile yarns or wrapping tissue films, and similar tough, flexible structures.

The present application relates to a similarly satisfactory dissolution of polyacrylonitrile in an organic solvent taken from a different class of organic compounds and the polyacrylonitrile solutions produced thereby are similarly satisfactory for the production of tough, flexible, dense, colorless yarns and films which are suitable for use in practically all general commercial applications of such products.

It has been known heretofore that concentrated, aqueous solutions of inorganic salts such as lithium bromide, zinc chloride and sodium sulfocyanide will dissolve polyacrylonitrileand it has been proposed (Rein U. S. Patent No. 2,140,- 921). to employ the resulting solutions in the formation of yarns and films. been found substantially impossible to use the resulting compositions in such a manner. Their However, it has extrusion into coagulating baths of the type proposed (including such non-solvents for'acrylonltrile as water, dilute acid, dilute salt'solutions, etc.) result in the formation of shaped articles that contain large amounts of the inorganic salt of the proposed solvent." These salts are distributed throughout the structure and destroy the continuity of the polyacrylonitrile phase and the structure possesses poor physical properties. Removal of these salts, when possible, results in the formation of a porous-spongy, weak, undesirable structure that is very brittle and completely unsuited for use as a yarn or film. Moreover, when it is attempted to form a multifilament yarnby extruding, for example the proposed aqueous sodium sulfocyanide polyacrylonitrile composition, into a. dilute acid bath, it is found that .the individua1 filaments obtained stick together-Ito. form an essentially monofilament structurethatis extremely brittle and'cannot be bent'br worked without breaking. v

U. S. Patent No. 2,167,537 to Tobis points out that certain copolymers of acrylonitrile and an acrylic acid ester (those copolymers containing not more than of acrylonitrile) are soluble in mixtures of organic solvents such as dioxan, monochlorbenzene, cyclohexanone, etc. However, these liquids are incapable Of dissolving or even swelling polyacrylonitrile or copolymers of acrylonitrile containing higher percentages of acrylonitrile, i. e. acrylonitrile polymers 01. the type with which this invention is concerned. As previously mentioned, polymers containing such high percentages (at least by weight) of acrylonitrile are especially desirable for use because of their good physical properties and excellent chemical resistance.

It has also been proposed (Rein U. S. Patent No. 2,117,210) to dissolve polyacrylonitrile in molten quaternary ammonium salts such as benzyl pyridinum chloride, an ionizable salt. Although the resulting solution can allegedlybe used to form yarns or films of polyacrylonitrile, the solution itself is dark red to brown in color, indicating that some decomposition of the polyacrylonitrile or some reaction between the polyacrylonitrile'and the molten salt has probably taken place. 1 Such solutions are not satisfactory for the production of commercially useful, shaped articles of polyacrylonitrile. Here again, it has been found practically impossible to obtain filamentary structures such as yarns from the composition. Films or filaments, when obtainable, are extremely brittle; they are highly colored and very weak, presumably because of the pres- 3 ence within them of residual quaternary ammonium salt. Removal of this salt is difficult and the resulting structures contain numerous and large voids that make the structures substantially useless for commercial purposes.

It is therefore an object of this invention to dissolve polyacrylonitrile or a copolymer or indecompose the polymer, the solution being suitable for the formation of commercially useful, void free articles of polyacrylonitrile, for example yarns which are suitable as textile yarns andfilms which are, suitable as wrapping tissue.

It is another object of this invention to produce a solution of polya'crylonitrile, or a copolymer or interpolymer of acrylonitrile in which at least 85% by weight of the polymer is acrylonitrile, in a volatile organic solvent, which solution is stable over'extended periods of time and is eminently suited for use in the manufacture of shaped articles such as' yarns, films. tubes, straws,

artificial horsehair, bristles and ribbons, or when highly concentrated, for use in the manufacture of molded articles.

It is a still further object of thisinvention to produce shaped articles and structures of polyacrylonitrile, or copolymers or interpolymers of acrylonitrile in which at least 85% by weight of the polymer is acrylonitrile.

It is still another object of this invention to produce a shaped article or structure of polyacrylonitrile or copolymers or interpolymers of acrylonitrile in which at least 85% by weight of the polymer is acrylonitrile, for example a yarn, film, tube, bristle or the like which is tough, flexible, tenacious and free from voids.

Other objects of the invention will appear hereinafter.

The objects of the invention may be accomplished in general by dissolving polyacrylonitrile, or a copolymer or interpolymerof acrylonitrile in material which will undergo hydrogen bonding with the active hydrogen-bonding groups of the polymer molecules and thus weaken the strong hydrogen bond within the polymer molecules and cause the hydrogen-bonding forces to be shared between molecules. of the polymer and the solvent. In this manner, it is possible to form a molecular dispersion of the polymer within the solvent and thus form a solution.

However, the strength of the hydrogen-bonding capacity cannot be taken as the sole criterion as to whether or not a compound will function to dissolve an acrylonitrile polymer. It is also necessary that, in order to function as a solvent for an acrylonitrile polymer, the compound contain certain groups which will be capable of catisfactorily sharing a hydrogen bonding force with the particular active group of the acrylotrile polymer. In most instances, these groups require the presence of a hydrogen atom on a carbon atom to which the group is attached (designated as an alpha-hydrogen atom). Such groups as require the alpha-hydrogen atom are ineffective to impart solvent power if the alphahydrogen atom is missing.

It has now been found that groups capable of conferring solvent power include dimethyl carmyl I formyl imido which at least 85% by weight of the polymer is acrylonitrile in di-substituted formamide of the type more specifically defined hereinafter.

If the solvent has a relatively low boiling point (less than about 250 C.), the solution of polyacrylonitrile may then be formed into a shaped structure, for example a yarn or film and the solvent removed from the shaped structure. When the solvent is relatively non-volatile and has a boiling point of about 300 C. or more, shaped articles may be made from the solution and at least a portion of the solvent may be retained therein as a plasticizer for the articles.

It has been recognized in recent years that under certain conditions, an atom of hydrogen is attracted by rather strong forces to two atoms instead of only one so that it may be considered to be acting as a bond between them. Thi is called the hydrogen bond.

The difllculty of dissolving polymers containing at least 85% by weight of acrylonitrile is due to the presence within the molecules of strong hycyano (45m, thiocyano (-s-o-Em and CH: O C formyl imido (HCON cyanomethylene CHCN) thiocyanomethylene CHSCN) and sulfoxyand CHSO2O) shall hereinafter be referred to as solvogenic groups and compounds containing them are frequently capable of dissolving an acrylonitrile polymer containing at least 85% by weight of acrylonitrile.

In the event that two or more groups requiring the presence of an alpha-hydrogen atom in order to render them soivogenic are attached to the same carbon atom and compete with each other for an available'alpha-hydrogen atom, the sulfoxy group, the cyano group and the thiocyano group take preference over each other in the order Representative compounds coming within the named to form the solvogenic roup. the lower scope of the above formula and suitable for use rankin r p or o p pr ent sum n m ly as solvents for the above-mentioned acrylonitrile the nature of an inert substituent on the carbon polymers include:

atom. 5 0 0 ON It has furthermore been found that compounds ll m containing the above-mentioned solvogenic HC-N groups will be solvents for the above-mentioned CHICN polymers only if the carbon content of the compound be within certain limits as given below. If N'N'biswymmathyl) the ratio of carbon to solvogenic groupings is p 0 cmomcN maintained within the said limits, the compounds JL will retain solvent properties of the polymer even though the molecule be of considerable size and 031011101? complexity. 'Ifhe solvent power of the compound N'Nmis (bemwmoethyl) Mmmide for acrylomtrile polymers 15 increased if add1- tional solvogenic groups are present in the molecomomsmomcn, 0 ular structure of the compound, the effect of r t H these groups being additive.

It has now been found that formamide (formyl v N I imido) derivatives which are fusible without deb t th ta th In" 1 th I composition, preferably those having a melting e Hyanoe ibm fiid e H We y) point below 250 0., in which both valences of the N-atom of the amide are satisfied by hydrocmsoflcmom 0 carbon carbon atoms and which are embraced by N-C-H the following empirical formula will dissolve poly- NC CH g I I acrylonitrile and copolymers and mterpolymers in which at least 85% by Weight of the polymer is N-(beta-cyanoethyl)-N-(beta-methylsulfonylethyl) acrylonitrile: mmmde CH3 v O [o.( o-N ][0,( 2-05N) ][C,( /?-SCEN) 10.x. o. N N

( CHa n H wherein X represents 0 o O om msmcmom (H OH O, CH O. oH-zL, or CH- CH g No-omo N-(beta-cyenoethyD-N-(beta isopropylsullonylethyl) the free valance of the sulfoxy group being at- 40 formamide tached also to carbon; cmcmomsoiomcm 0 t is an integer equal to or greater than 1; m, q, u and w are integers equal to or greater than N C-CHzC zero,

m+q+u+w+t is equal to or greater than 2;

N-(beta-cyanoethyD-N-(beta-n-propylsullonylethyl) formamide n, p, r, v and k are mtegers equal to or greater than zero; omomsocmom 3 provided always that a C .H k/t is equal to or less than 3; Nc-cmo 1 12/10 is equal to or less than 2; ggiggiggw W r/u is equal to or less than 0.5; Y

p/q is equal to or less than 1.5 and n/m is equal to or less than 1.5. CH

These compounds are not salts but may be NC CHZC cyclic or acyclic and may possess one or more ethylenic or acetylenic linkages. Valences other N (bem cymethy1)fom(:gigmthylsumnylethyl) than those contained. in carbon-to-carbon link- CH, ages and not shown as satisfied in the above formula must be satisfied by hydrogen, halogen, oxy- CEMHSO 0155015 0 gen or bivalent sulfur atoms or by hydroxyl, thiol, N-o-H cyano, thiocyano or sulfoxy groups; the total NC CH2C I number of such halogen, oxygen, hydroxyl' and thiol substituents not exceeding one half the sum m+l1+u+w+t and the number of cyano, Cmcmcmsocmcm 0 thiocyano and sulfoxy groups not exceeding the N-(beta'cyanoethyD-N-(beta-isopropylsulflnylethyl) formamide sum m+q+u+w+t. The respective tolerances of g are independent of each other and members of N-(beta-cyanoethyD-N-(beta-qi-propylsulfinylethyl) both groups may be present in the molecule up to their group tolerances. The substituent oxy- NCS-CECH 0 gen or sulfur atoms may appear in the com- NCH pound as bivalent groups either as a side group Ncqmmfiz (carbonyl or thiocarbonyl) or within the chain such solutions into an evaporative or coagulative medium. By forming the structures in an evaporative medium, the solvent must be evaporated therefrom and by forming th structures in a coagulative medium, the solvent should be removed by selective solution in a non-solvent for the polymer.

The solutions are prepared by dissolving the polyacrylonitrile, or copolymer or interpolymer of acrylonitrile with one or a mixture of the abovementioned solvents. Som of these solvents are solid at ordinary temperatures and dissolve or retain the polymer in clear solution only at elevated temperatures, for example at temperatures of 100 C. or higher, below which temperature-the composition resembles a gel. In all cases when the polymer is dissolved in a solvent of the above class, the resulting composition while hot has the appearance of a true solution. When cooled to room temperature, the composition generally takes on the appearance of a gel, which gel may, on standing, undergo syneresis. Reheating of this gel or syneresed mass however causes it to again return to solution form.

In view of the relatively high melting points of some of the solvents of this invention, they would have comparatively little use in the production of a polyacrylonitrile spinning or casting solution.

Such solvents are, however, excellent solvent plasticizers for polyacrylonitrile since they are soluble in a wide range of proportions with the said acrylonitril polymers. The present invention therefore contemplates solid solutions of acrylonitrile polymers containing at least 85% by weight of acrylonitrile as well as liquid solutions thereof.

Shaped articles obtained from solvent solutions of polyacrylonitrile in accordanc with the invention and from which the solvent is subsequently removed are substantially free of foreign matter and voids and substantially undecomposed and chemically unchanged from the simple polymer prior to its solution.

The above-described organic solvent solutions of acrylonitrile polymer may be shaped in the form of filaments, yarns, films, tubes and like structures by apparatus and processes generally known in the art, the detailed operating conditions being suitably modified.

Suitable methods and apparatus for the production of shaped articles of the polymers of this invention will be readily apparent by reference to the following detailed description when taken in connection with the accompanying illustrations ,in which:

Figure 1 is a diagrammatic vertical sectional view showing a dry spinning cell suitable for use in accordance with the invention;

Figure 2 is a diagrammatic perspective view showing a yarn drawing device for use in connection with the invention:

Figure 3 is a diagrammatic perspective view showing a wet spinning apparatus for use in the invention; and

Figure 4 is a diagrammatic side elevational view,

showing a suitable film casting apparatus for use in accordance with the invention.

Referring to Figure 1 of the drawing, reference numeral H designates a spinneret through which a plurality of filaments l5 are formed by extruding a filament-forming solution supplied to the spinneret by means of conduit l3. The spinning cell is jacketed with a material I! such as a re- 14 iractory in which is embedded an electrical heating coil I9. The spinning cell can thus be operated at any desired temperature. conduits 2| are provided adjacent the bottom of the device for passing evaporative medium through the cell so as to evaporate the solvent from the extruded filaments IS. The evaporative medium is removed from the cell through outlet openings 23. The yarn comprising the plurality of filaments I5 is passed from the bottom 01' the spinning cell around guide roller 25 and is wound on a. bobbin 21.

Referring to Figure 2 of the drawing, the yarn I5 is removed from the bobbin package 2! and passed about draw roller 29 and separating roller 3|. From draw roller 29, the yarn is passed to a second draw roller 33 and separating roller 35. The yarn is passed around the two sets of draw rollers including-their separating rollers a sufilcient number of turns to prevent slippage of the yarn. Draw roller 33 isrotated at a greater speed, for example three to ten times the speed of draw roller 29. In this manner, the yarn I5 is stretched between the two draw rollers. As the yarn passes between the two draw rollers, a heating medium is brought into contact with the yarn through blower nozzles 31 and 39. The yarn passing from the draw roller 33 is wound on bobbin 4|. The drawingor stretching of the spun yarn as described is not claimed as part of the present invention, but is claimed in the copending application of Daniel T. Meloon, Serial No. 496,397, filed July 28, 1943.

Figure 3 of the drawing illustrates a wet spinning apparatus for the production of yarn, The acrylonitrile polymer solution is passed through conduit -5I and is extruded through spinneret 53 to form a multifilament yarn 54. The yarn 54 is passed about guide roller 51 which is positioned within the coagulating liquid in tank 55. The yarn is then passed about guide roller 59 and is wound on bobbin 6|. I

The organic solvent solution of polyacrylonitrile may be cast in the form of a film as illustrated in Figure 4. In accordance with this apparatus, the polymer solution is passed from hopper H on to the endless steel band 13 where it is smoothed by means of a doctor knife 15. The band, together with the film, is passed under a means 11 for bringing a heated drying medium into contact with the film. The film 8| is pulled from the band 13 and collected on a mill roll 83..

The polyacrylonitrile for use with the invention is preferably prepared by the ammonium persulfate catalyzed polymerization of monomeric acrylonitrile dissolved or emulsified in water. It can, however, be prepared by any other suitable type of polymerization reaction such as, for example, the emulsion type reaction disclosed by U. 8. Patent No. 2,160,054 to Bauer et al. The polymer preferably possesses a molecular weight within the range of 15,000 to 250,000 or even higher, as calculated from viscosity measurements by the Staudinger equation:

Molecular weight= i%, wherein:

N,,,=specific viscosity= and viscosity of solution viscosity of solvent A plurality of polymer.

acrylonitrile of Example I were intimately mixed with 25 parts of solid N,N'-diformyl piperazine and heated to a temperature of 170 0., to form a viscous, homogeneous mass or solution. Subsequent cooling of this solution to room temperature resulted in the formation of a gel-like mass .of high viscosity which could be molded to a strong, tough, rod-like structure.

As indicated in the above examples, it is' possible by the practice of this invention to obtain a solution of polyacrylonitrile, or'a copolymer or in-terpolymer of acrylonitrile which iseminently ing the above said molecular weight will precipitate from the solution. Increasing or decreasing the amount of the catalyst, while maintaining the other conditions constant, decreases or increases the molecular weight of the polymer. Acrylonitrile copolymers and interpolymers containing at least 85% by weight of acrylonitrile and likewise preferably having .a molecular weight of 15,000 to 250,000 orhigher'can be prepared in a similar manner.

The following examples in which parts, proportions and percentages are by weight unless otherwise specified illustrate preferred methods of preparing solutions of polymers in accordance with the principles of this invention and of employing these solutions in the manufacture of commercially satisfactory shaped articles of the The invention is not to be limited by the details set forth in the examples.

Example I Fifteen (15) parts of ,a polyacrylonitrile prepared by the polymerization of monomeric acrylonitrile in accordance with the teachings of U. S. Patent No. 2,160,054 to Bauer et a1. and possessing an average molecular weight of 120,000 as determined by the Staudinger equation from viscosity data are ground to an average particle size of 200 mesh and mixed with 85 parts of N-betacyanoethyl-N-methyl formamide, the resulting mixture being heated within a period of fifteen minutes to a temperature of 150 C. to form a clear, viscous solution which may be used at this temperature for the casting of films. If subsequently cooled, the solution becomes more viscous.

The solution was heated to a temperature of 175 0., cast on to a surface heated to 175 C. and dried to form a thin, transparent film of acrylonitrile polymer, the film being tough, flexible and tear resistant. 7

Example 11 Twenty (20) parts of a copolymer consisting of 90% of acrylonitrile and 10% of vinyl thiolacetate prepared by the aqueous emulsion polymerization of acrylonitrileand vinyl thiolacetate in .jected to a tension of 0.7 gram per denier (based on the final yarn denier) during its travel through the bath. The solvent was removed ,from the yarn by the glycerol, thereby coagulating the copolymer.

' Example l1! Seventy-five ('75) parts of the powdered polysuited for use in the manufacture of shaped articles such as yarns, films, or molded, articles. These solutions are also suited for use as lacquers or coating compositions.

where the high chemical and electrical resistance of the polymer is important.

For the purpose of definition, a solvent is a material which, when in the liquid state, is capable of forming solutions in which the polymer is present in a concentration by weight of 5% or more. In most instances, the polymer is soluble in almost all proportions although the miscibility may take place at elevated temperatures in the case of certain compounds.

As also shown, the solvents of the invention are useful not only in connection with polyacrylonitrile, but also with copolymers and interpolymers of acrylonitrile and other polymerizable substances such as, for example, compounds containing one or more ethylenic linkages including vinyl and acrylic compounds as well as olefinic or dioleflnic hydrocarbons such as isobutylene, butadiene, etc. They are eminently satisfactory for use with those polymers that contain an appreciable amount of acrylonitrile, for example, polymers, copolymers and interpolymers that contain at least 85% by weight of acrylonitrile and that have generally been regarded by the art as being completely insoluble in all common organic solvents. Nor are these solvents limited to use with a polyacrylonitrile of any given molecular weight. They can be used with a polymer of almost any given molecular weight and are especially satisfactory for use with those polymers having an average molecular weight within the range 15,000 to 250,000 as determined by viscosity data using the Staudinger equation and intended for use in the manufacture of yarns or films.

The solution of acrylonitrile polymer dissolved in an organic solvent in accordancev with this invention must be of such a concentration that its viscosity at the operating temperature is within a workablerange. When it is to be employed in the spinning of yarn or the casting of film, the solution should preferably have aviscosity within the range 25 to 750 poises. has a molecular weight of 250,000 or more, this requires that the maximum concentration of polymer in the spinning solution be of the order of 10%. Generally, it is preferred that the spinning solution contain at least 10% of the polymer because of the difiiculty of rapidly removing large amounts of solvent from the solution in the spinning operation. Moreover, it is economically undesirable to use such large amounts of solvent for the spinning of a given amount of polymer although it'is true that the solvent can be completely recovered from the spinning operation and reused. For these reasons, it is preferred to employ a polymer having an average molecular weight of between 40,000 and 150,000'

since such a polymer forms a solution of the de- ,They are especially. .useful in the coating of wire and electrical parts When the polymer 1 sired viscosity in concentrations of the order of to 25% and at a desirable spinning temperature of the order of 100 to 150 C. 01 course, it is within the scope of the invention to heat the solution to a higher temperature, even to above the normal boiling point of the solvent, for the actual spinning operation. Here again, the controlling factor with regard to the temperature of the spinning solution is the viscosity of the solution.

The evaporative medium employed in th dry spinning of filaments and yarns or the dry casting of films in accordance with this invention may be any vapor inert to the filmor filamentforming solution such as air, nitrogen, steam, etc., or any suitable mixture thereof. The temperature of the evaporative medium is dependent on such factors as the dimensions of the spinning cell, the composition and rate of extrusion of the spinning solution and the rate of flow of the evaporative medium. It is only'necessary that these several factors be so correlated that the yarn or other shaped article leaving the spinning cell be sufliciently freed of the solvent so that it is solidified and capable of being wound into package form or otherwise collecte As indicated in Example II above, shaped articles of acrylonitrile polymer can also be formed by extruding the spinning solution into a suitable precipitating bath comprising a liquid that is miscible with the solvent but is a chemically inert non-solvent for the acrylonitrile polymer, iAS examples of such a liquid maybe mentioned water, glycerin, organic solvents such as alcohol, ether, etc., or aqueous solutions of salts, alkalies or acids, The copending application of William W. Watkins, Serial No. 496,376, filed July 28, 1943, covers the use of glycerol and aqueous solutions of salts as baths, preferably at elevated temperatures, for the wet spinning of acrylonitrile polymer yarn, from solutions of the polymer, preferably with substantial tension and stretch being applied during spinning.

The article of acrylonitrile polymer thus obtained can advantageously be subjected to a stretching operation of the type employed in the above examples. This stretching is preferably performed by passing the yarn between two positivel driven rollers, the peripheral speeds of which are so adjusted that the article is stretched from two to ten times its original length, preferably approximately six times its original length. This stretchin of the formed article may be per. formed at any suitable time. However, in the case of articles formed by the wet spinning or casting technique, it is preferably performed before the article has been completely dried. The orientation of the structure thus obtained improves the physical properties of the structure including its tenacity, its resilience, etc.

This stretching of the shaped article can also be accomplished b causing the article, while passing between stretching rollers, to contact a heated stationary pin or to pass through an inert medium such as air, water, glycerin, etc., heated to a high temperature, Obviously, the article must not be exposed to this high temperature for a period sufl'iciently long to decompose the polymer. In general however, the time of contact of the article with the heated medium is so short that temperatures up to 250 C. can be employed. Although it is generally preferred to heat the article to a temperature of at least 100 C. during thest-retching operation, this is not essential. Desirable results can be obtained by stretching invention, when present in small amounts, can

also be used as plasticizing agents for the polymer and the higher boiling compounds of the invention are especially suited for such use. At the same time, it is, of course. to be understood that non-solvent softeners, such as glycerol, can also be incorporated in the solutions of the invention, these materials remaining in the subsequently formed articlesto impart a softening effect. If it is desired to use such plasticizing or softening agents with polyacrylonitrile, they are preferably added in the desired amount to an already formed solution of the polymer in a lower boiling solvent, for example to a solution of the polymer in dimethyl formamide,

This invention is primarily concerned with the steps or dissolving polyacrylonitril in a uitable solvent to form a stable solution adapted for use in the manufacture of shaped article of polyacrylonitrile. It is characteristic of the invention that the solutions provided by it are stable; the solvents do not cause a decomposition or chemical alteration of the dissolved acrylonitril polymer. At the same time, it is also characteristic that the solvents provided by the invention are also useful in the dissolving of mixtures of polyaerylo. nitrile and adluvants such as dye modiriers, linear polyamides such as nylon, derivatives of cellulose including cellulose ethers and esters, polymers of vinyl compounds such as vinyl chloride, vinyl acesate, acryli acid, etc., which adjuvants may be incorporated in the acrylonitrile polymer solution to niodify the properties, both chemical and physical; of the resulting shaped articles.

This invention provides a class of solvents for polyacryionitrile, andcopolymers and interpolymers of acrylonitrile which were heretofore considered substantially insoluble. The solvents are capable of forming with the polymer clear solution that are stable for extended periods of time and are admirably suited for use as lacquers or coating compositions or in the manufacture of shaped articles of the polymer, for example by extrusion into an evaporative or coagulative medium, orby the use of a molding technique.

The invention also provides a class of materials that is eminently suited for use in plasticizing structures comprising the acrylonitrile polymers. The materials provided by this invention are apparently true solvents for the above-mentioned acrylonitrile polymers. They do not tend to react with or decompose the polymer, the polymeric material obtained from the solution of this invention apparently being the same identical chemical composition as the initial polymer.

Yarns, films and similar articles of polyacrylonitrile prepared from the solutions of this invention can be stretched to yield oriented structures that possess a high tenacity, a desirable elongation and a high elastic recovery that compares favorably with that of silk. The articles are not contaminated with undesirable salts and they are substantially free of void spaces.

Reference throughout the specification and claims, to acrylonitrile polymers, polymers of acrylonitrile, and co-polymers and interpolymers of acrylonitrile "containing at least by weight of acrylonitrile" signifies polymers containing in their molecules at least 85% by weight described herein except as set forth in the apthe free valences of the sulioxy group being atil,404,788 19 a g 20 of the acrylonitrila unit which is considered to 5. A new composition of matter -as defined in be present in the polym r molecule a the group claim 1, in which the polymer solution has a 6 viscosity within the range 25 to 750 poises.

H;- E- N 8. As a new composition of matter, a polymer that is. at least 85% by weight of the reactant 6 of acrylonitrile containing-in the polymer molematerial converted into and forming the polymer l atlea t 85% by wei ht O crylonitrile disis acrylonitrile. solved in N-beta-cyanoethyl-N-methyl forma- Since it is obvious that many changes and mide. I modifications can be made in the above described 7- A a w omp on of matter, a polymer details without departing from the nature and 10 of acryl t i c ntaining in th polymer molespirit of the invention, it is to be understood that cule at least 85% by weight of acrylonitrile and the invention is notto be limited to the details an organi comp embrwed by the formula;

wherein it is a member of the class consisting of pended claims. I o o 0 0 I claim: g H a H 1. As a new composition of matter, a polymer CH- 0, CH- -O', /(?n and/OE- of acrylonitrile containing in the polymer molecule at least 85% by weight of acrylonitrile dissolved in an organic compound embraced by the formula:

wherein X is a member of the class consisting of trogen atom of the formyl imido group are ato o 0 o tached to hydrocarbon carbon atoms; t is an integer at least equal to 1; m. 11. u and w are in- P L tegers at least equal to zero; m+q+u+w+t is at least equal to 2; n, p, r, v and 7c are integers at the free valences of the s ulfoxy group being at- 25 tached also to carbon; both valences' of the nitached also to carbon; both valences ofthe vnido s n t xce d ;)lu does not exceed 0.5; p/q trogen atom of the formyl imido group are atdoe not exceed 1.5 and 11/111 does not exceed 1.5, tached to hydrocarbon carbon atoms; t is an inall valenoes of said compound other than those teger at leastequal to 1; m, q, u. and w are incontained in carbon-to-carbon linkages and not tegers at least equal to zero; m+q+u+w+t is at shown as satisfied in the formula being satisfied least equal to 2; n. p. v and k are integers at by a substituent taken from the group consisting least equal to zero; k/t does not exceed 3; 12/10 of hydrogen, halo xygen, bivalent sulfur, does not exceed '2; 'r/u does not exceed 0.5; PM hydroxyl; thiol, cyano. thio yano. and sulfoxy; does not exceed 1.5 and n/m does not exceed 1.5. the total number 01 such h oxygen, sulfur, all valences of saidcompound other than those hydroxyl and thiol substituents not exceeding contained in carbon-to-carbon linkages and not one half m-i-q+ +w+t and the total number of shown as satisfied in the formula, being satisfied cyano, thiocyano and sulfoxy substituents not by a substituent taken from the group consisting so exceeding m+q+u+w+t of hydrogen, halogen, oxygen, bivalent sulfur, hydroxyl, thiol, cyano, thiocyano and sulfoxy; solution contains at least 10% of said polymer the total number of such halogen; oxygen, sulof acrylonitrile.

- fur, hydroxyl and thiol substituents not exceed- T c mp i i n 01 claim 1 in which the ing one half m+q+u+w+t and the total numu polymer of acrylonitrlle is polyacrylonitrile havber of cyano, thiocyano and sulfoxy substituents ing a molecular weight between 15,000 and not exceeding m+q+u+w+t. 250,000.

2. A new composition of matter as defined in 10. The composition of claim 1 in which the claim 1, in which the polymer is polyacrylonitrile. polymer of acrylonitrile is polyacrylonitrile hav- 3. A new composition of matter as defined in so ing a molecular weight between 40,000 and claim 1, in which the polymer has a molecular 150,000. weight of between 15,000 and 250,000. 11. The composition of claim 'U'in which the 4. A new composition of matter as defined inpolymer of acrylonitrile is polyacrylonitrile. claim 1, in which the polymer has a. molecular i weight ofbetween 40,000 and 150,000. RICHARD R.

least equal to zero; k/t does not exceed 3; 12/10 8. The composition of claim 1 in which the Q Certificate of Correction Patent No. 2,404,723. July 23, 1946.

RICHARD R. MERNER It is hereby certified that errors appear in the printed s ecification of the above numbered patent requiring correction as follows: Column 2, ine 41, for pyridinum read fiyridinium; column 5, lines "32 to 34 and column 19, lines 27 to 29 inclusive,

right (1 portion of the formula, for the last five indistinct subletters read u, v, w, k and t respectively; column 5, lines 30 to 32, right hand portion of the formula, for

read N-ii-N N -.g

column 7, line 56, for aminoethyl) read aminoethyl]; column 10, line 57, for CH CH CN read 0H20H20N; column 20, line 17, in the formula, for the indistinct subletter before the last double bracket read u; line 15 same formula, after C between the last pair of brackets, for the indistinct subletter read 1); and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 15th day of October, A. D. 1946.

LEsLn FRAZER.

First Assistant Commissioner of Pafc'nta. 

